The application field of Ethernet (registered trademark; hereinafter omitted) has widely expanded due to its various advantages as a communication standard. For example, Ethernet starts to be used not only in so-called an information system for office use, but also in a system for industrial use. Ethernet used in the system for industrial use is generally called “industrial Ethernet”. The industrial Ethernet, which is based on an Ethernet technology, has a function of realizing real-time response performance required in the system for industrial use. For the industrial Ethernet, ten or more different standards have been created by various standards groups including IEC (International Electrotechnical Commission). In recent years, new industrial Ethernet standards are created in association with Smart Grid.
A common physical layer is adopted in the industrial Ethernet, so that nodes can physically be connected by plugging cables into each other. However, in the case where the physically-connected nodes conform to different industrial Ethernet standards, one node may transmit data to a transmission destination node with a rule different from the rule specified by a control protocol of the industrial Ethernet that the connection destination node uses. In this case, the one node (transmission source node) transmits data at an unexpected timing and in an unexpected format to the transmission destination node. In the case where nodes that conform to different industrial Ethernet standards are connected to each other in one system as described above, the system may be confused.
Although the industrial Ethernet standards have been exemplified in the above description, such a problem is not limited to the industrial Ethernet standards. That is, it can be considered that such a problem occurs when nodes that conform to different Ethernet standards are connected to one system.